The present disclosure relates to an aqueous electrolyte. The present disclosure further relates to the use of the aqueous electrolyte in a supercapacitor, in a pseudocapacitor or in a hybrid supercapacitor. Finally, the present disclosure relates to a hybrid supercapacitor containing the aqueous electrolyte.
Electrochemical energy stores already play an important role in present-day society and will in future become even more important due to the increasing use of alternative energy sources and due to increasing electrification of the automobile industry. Apart from batteries, capacitors are used in particular as electric energy stores. Apart from classical capacitor designs, supercapacitors, pseudocapacitors and hybrid supercapacitors, inter alia, are used today. For the purposes of the present disclosure, supercapacitors are double-layer capacitors in which the electrolyte is the conductive connection between two electrodes. The electrodes consist of carbon or derivatives thereof having a very high static double-layer capacitance. The proportion of faradaic pseudocapacitance in the total capacitance is only small. Pseudocapacitors store electric energy with the aid of reversible redox reactions at electrodes suitable for this purpose. Hybrid supercapacitors (HSC), for example lithium ion capacitors, can use mixtures of a plurality of chemical substances having both faradaic materials and also capacitively active materials as electrode material. The electrodes obtained in this way are referred to as hybridized electrodes.
S. T. Senthilkumar, R. Kalai Selvan, Y. S. Lee, J. S. Melo, Journal Mater. Chem. A, 2013, 1 1086, describes adding a halogen iodide to the electrolyte in order to increase the capacitance of such capacitors even further. Here, pseudocapacitive reactions in which three iodide ions are oxidized to a triiodide ion occur.